From 309bef4db7211fe48ba6cfd7bdbd63258f147dcb Mon Sep 17 00:00:00 2001
From: Maurice <mauriceboe@icloud.com>
Date: Wed, 14 Oct 2026 23:37:58 +0200
Subject: [PATCH] fix(ferratas): leaving 3D with via ferratas on no longer
 crashes, the removed map is not asked for its layers

---
 .../Ferratas/useFerrataLayerGL.test.tsx       | 20 ++++++++++++++++---
 .../components/Ferratas/useFerrataLayerGL.ts  |  3 +++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/client/src/components/Ferratas/useFerrataLayerGL.test.tsx b/client/src/components/Ferratas/useFerrataLayerGL.test.tsx
index bedd48353..507503f35 100644
--- a/client/src/components/Ferratas/useFerrataLayerGL.test.tsx
+++ b/client/src/components/Ferratas/useFerrataLayerGL.test.tsx
@@ -1,5 +1,5 @@
 /**
- * FE-FERRATA-GL-001 to FE-FERRATA-GL-012: the via ferrata layer on a
+ * FE-FERRATA-GL-001 to FE-FERRATA-GL-013: the via ferrata layer on a
  * MapLibre or Mapbox GL map.
  *
  * Pinned: the layers go in once per map (and wait for `idle` when tiles are
@@ -64,7 +64,7 @@ function fakeGlMap(styleLoaded = true) {
   const images = new Set<string>();
   const handlers = new Map<string, Set<Handler>>();
   const once = new Map<string, Set<Handler>>();
-  const state = { styleLoaded, hit: null as null | { properties: { id: string; group: string } } };
+  const state = { styleLoaded, removed: false, hit: null as null | { properties: { id: string; group: string } } };
   const canvas = document.createElement('canvas');
   const container = document.createElement('div');
   const keyOf = (type: string, layer?: unknown) => (typeof layer === 'string' ? `${type}:${layer}` : type);
@@ -77,7 +77,12 @@ function fakeGlMap(styleLoaded = true) {
     removeSource: vi.fn((id: string) => {
       sources.delete(id);
     }),
-    getLayer: vi.fn((id: string) => (layers.has(id) ? {} : undefined)),
+    // Like MapLibre: a removed map has no style, and asking it for a layer throws.
+    getStyle: vi.fn(() => (state.removed ? undefined : { version: 8 })),
+    getLayer: vi.fn((id: string) => {
+      if (state.removed) throw new TypeError('can\'t access property "getLayer", this.style is undefined');
+      return layers.has(id) ? {} : undefined;
+    }),
     addLayer: vi.fn((spec: { id: string }) => {
       layers.add(spec.id);
     }),
@@ -267,6 +272,15 @@ describe('useFerrataLayerGL', () => {
     expect(() => renderHook(() => useFerrataLayerGL(null, GROUPS, vi.fn()))).not.toThrow();
   });
 
+  it('FE-FERRATA-GL-013: a map already removed with its view (leaving 3D) is left alone on unmount', async () => {
+    const gl = fakeGlMap();
+    const { unmount } = render(<FerrataLayerGL map={gl.map} groups={GROUPS} onSelect={vi.fn()} />);
+    await waitFor(() => expect(gl.layers.has(LABEL)).toBe(true));
+    gl.state.removed = true;
+    expect(() => unmount()).not.toThrow();
+    expect(gl.listeners()).toBe(0);
+  });
+
   it('FE-FERRATA-GL-010: a theme change repaints the installed layers without rebuilding them', async () => {
     const root = document.documentElement;
     root.style.setProperty('--map-ferrata', 'black');
diff --git a/client/src/components/Ferratas/useFerrataLayerGL.ts b/client/src/components/Ferratas/useFerrataLayerGL.ts
index 4cc358a00..ef31a9d9f 100644
--- a/client/src/components/Ferratas/useFerrataLayerGL.ts
+++ b/client/src/components/Ferratas/useFerrataLayerGL.ts
@@ -136,6 +136,9 @@ function addFerrataIcon(map: Map, paint: FerrataPaint, gone: () => boolean): voi
 }
 
 function removeFerrataLayers(map: Map): void {
+  // A map already removed with its view (leaving 3D) took its style and the layers with it;
+  // asking it for a layer then throws.
+  if (!map.getStyle?.()) return;
   for (const layer of [...LAYERS].reverse()) if (map.getLayer(layer)) map.removeLayer(layer);
   for (const source of [LABEL_SOURCE, SOURCE]) if (map.getSource(source)) map.removeSource(source);
   if (map.hasImage(FERRATA_ICON_IMAGE)) map.removeImage(FERRATA_ICON_IMAGE);